When a fluid, having uncontrollable velocity, impinges upon a power extracting impeller, for example, a high wind impacting a wind turbine, excessive loads may have to be absorbed by the impeller and supporting structure unless means are available to spill excessive loads. In conventional wind energy conversion systems, such as horizontal axis turbines operating on a tower or such as vertical axis wind turbines, load control is achieved generally by means of complex rotor blade pitch change mechanisms and/or powered yaw drives to yaw the rotor disc plane approximately (parallel) to the wind and/or application of large capacity brakes to the rotor drive shaft assembly to stop the rotor rpm. Regardless of which of the previous means of load control is applied, the rotor blades are still exposed to the severe fluid or wind velocity and, although loads on these blades are reduced, these rotors must deal with substantial survival fluid velocities and resulting stressing. Furthermore, since cost of energy produced by energy conversion systems is dictated in part by system capital cost, requirements of complex, large capacity and thus costly control subsystems, as described previously, adversely impact cost of energy.
A simple cost effective means of rotor load control is presented whereby, for TARP mounted twin interconnected rotor-generator assemblies located in TARP high fluid velocity fields, via creating rotor assembly thrust force differential between substantially diametrically oppositely located rotor assemblies causes said rotor-generator assemblies to subsequently yaw out of the high fluid velocity fluid stream and into shielded stagnation or low velocity wake flow fields about the TARP body.
Rotor thrust force differential means is achieved by one of several optional means, including: rotor speed changes such as slowing the rpm of one rotor-generator assembly relative to the other via application of a small mechanical or electrical brake to the rotor drive shaft assembly, which, unlike for conventional wind turbines for example, need not have the capacity to stop the rotor rpm under high torque or power conditions; or application of an electrical load change to one rotor-generator assembly relative to the other rotor-generator assembly causing thereby the former rotor to slow in rpm and consequently experience a thrust difference with respect to the other rotor; or activation of a drag device on one rotor-generator assembly such drag device, for example, being a TARP rotor strut vane pitchable surface; or activation of rotor blade pitch angle change on one rotor relative to the other. The noted optional means of rotor-generator assembly thrust differential actuation means can range from simple and economic to complex and costly. However, in either event, the proposed invention rotor load control is greatly superior over conventional system load alleviation means.
The present invention providing the process and means of TARP rotor system thrust, yaw and hence, load control means is henceforth designated as a TARP rotor system thrust, yaw and load control; i.e., TY&L control.